This invention relates to power supplies and, more particularly, to a fault-tolerant dual AC source redundant power supply system.
Power supplies may more precisely be called power converters because they receive a power source and change the source according to the demands of a load. For example, the power source may be a 120-volt alternating current (AC) power from an electrical outlet in a home or business and the load may be a personal computer motherboard requiring 5 volts of direct current (DC) power. Coupled between the source and load, the power supply is expected to reliably convert 120 volts AC to 5 volts DC.
The power supply typically includes a transformer, a rectifier, a filter, and a regulator. The transformer steps the incoming AC voltage either up or down and the rectifier converts the transformed voltage Into a pulsating unipolar (DC) voltage. The filter then smoothes out the voltage to a continuous one, and the regulator assures that a voltage within a certain range is supplied to the load at all times.
In addition to personal computers, many other power-consuming devices depend on power supplies for reliable operation. Mainframe computers, banking and traffic control systems, hospital equipment, emergency infrastructure, and security systems are but a few examples of systems in which disruption in service can be catastrophic or even life-threatening.
In such environments, power systems comprising multiple redundant power supplies may be used to avoid power disruptions. Such power systems are designed to connect to multiple power sources, and include circuitry for ensuring that, where at least one source is available, power to the load system remains uninterrupted.
The cost of redundancy, however, is not cheap. In a typical computer system, for example, a single power supply occupies a significant amount of space and generates enough heat to usually require its own fan. It is easy to understand why few stand-alone computer systems have redundant power supplies. For servers, mainframes, and other large-scale processing systems, however, redundant power supplies may be cost-justified, although these systems are often space-constrained as well.
Further, many power systems comprising redundant power supplies cannot conveniently be powered down for maintenance. If a component within the power system needs replacing, typically, it can only be replaced by turning the system off, e.g., removing the AC power source. This is the exact condition the power system was installed to avoid.
Thus, there is a continuing need to provide a power system comprising redundant power supplies, wherein the power system supports dual AC sources, is not prohibitive in size, and includes components that may be replaced while the system is operational.